Mobile Voice Core Expert
À1 Áúëãàðèÿ ÅÀÄ Top employer
more than 300 employees
Mobile Voice Core Expert
Ñîôèÿ
full-time

Mobile Voice Core Expert

Ñîôèÿ full-time

Job Description

Strength. Care. Growth
You’ll know A1 Bulgaria is the right place for you if you are driven by:

  • Opportunities to learn and build your career.
  • Meaningful work in a stable and fast-paced company.
  • Diversity of people, projects, and platforms.
  • A supportive, fun, and inspiring place to work.

Your daily routine would include:

  • Design, deploy, operate, and optimize IMS & VoLTE/VoWiFi/VoNR voice core platforms for all A1 OpCos.
  • Manage and optimize core elements, including P?CSCF, I?CSCF, S?CSCF, SBC, TAS, MRF, and MGW.
  • Ensure stability, performance, and high availability of voice services 24x7.
  • Troubleshoot complex SIP/Diameter signaling flows and perform root-cause analysis.
  • Support device testing, interoperability testing, regulatory feature validation (e.g., lawful interception, emergency call routing), and new service introduction.
  • Implement automation for configuration management, alarms, KPIs, and routine operational tasks.
  • Develop scripts and tools to improve core network reliability and operational speed.
  • Collaborate closely with vendors on upgrades, migrations, capacity expansion, and deployment of new features.
  • Contribute to the transformation toward cloud-native IMS and Voice over 5G (VoNR).

We’ll know you can make it if you have:

  • Strong expertise in 3GPP standards, IMS, VoLTE, VoWiFi, and SIP signaling.
  • Deep knowledge of Diameter, RTP/RTCP, and other telecom signaling protocols.
  • Familiarity with EPC and 5GC voice architecture and features, such as SRVCC and SMS over IP.
  • Experience analyzing packet captures using tools like Wireshark and vendor-specific trace tools.
  • Practical experience with automation tools, e.g., Ansible; Terraform is a plus.
  • Scripting skills in Python, Bash, or similar languages.
  • Ability to automate repetitive operational tasks and build dashboards or monitoring tools.
  • Hands-on experience with virtualized core networks (VMware, KVM).
  • Understanding of cloud-native architectures, containerization (Docker), and Kubernetes.
  • Familiarity with CI/CD pipelines, microservices, and Git-based workflows is an advantage.

Nice to Have:

  • Experience with 5G SA VoNR (IMS over 5GC).
  • Knowledge of CSFB, OMR, and supplementary services.
  • Hands-on experience with vendor platforms, such as Ericsson, Nokia, Mavenir, and Oracle SBC.
  • Exposure to observability and monitoring stacks, including Prometheus, Grafana, and ELK.
  • Experience building internal tools or APIs to support network operations.

Apply now!